media: cx231xx: Increase USB bridge bandwidth

The cx231xx USB bridge has issue streaming QAM256 DVB-C channels.
QAM64 channels were fine, but QAM256 channels produced corrupted
transport streams.

cx231xx alt mode 4 does not provide enough bandwidth to acommodate
QAM256 DVB-C channels, most likely DVB-T2 channels would break up
as well. Alt mode 5 increases bridge bandwidth to 90Mbps, and
fixes QAM256 DVB-C streaming.

Signed-off-by: Brad Love <brad@nextdimension.cc>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>